The present invention relates to a switch and, more particularly, to a switch provided with a negative pressure generator for producing a gas-blast flow toward the arc.
A conventional switch of this type is composed of a sealed container charged with an arc extinguishing fluid such as SF.sub.6 gas, a stationary contact and a movable contact provided in the container in such a manner as to be relatively separable from each other, a booster having a boosting chamber for boosting the arc extinguishing fluid by the energy of the arc produced by the separation of the contacts, and a negative pressure generator having a negative pressure chamber for producing a negative pressure by the relative movement of a cylinder and a piston induced by the separating operation of the contacts, as is disclosed in Japanese Patent Publication No. 16485/1987. To the arc between the separated contacts, a gas flow produced from the booster chamber toward the negative pressure chamber is blasted, thereby extinguishing the arc.
In a conventional switch provided with a booster and a negative pressure generator having the above-described structure, the negative generator is actuated from the initial stage of the cut-off operation, thereby producing a negative pressure. For this reason, the operating device of the switch must be so constructed as to produce a large operating force rapidly from the beginning of operation in correspondence with the negative pressure produced. This type of operating device, however, generally uses compressed air, so that it is difficult to obtain a large operating force at the initial stage of operation, as is known from the plenum characteristic thereof. On the other hand, use of an operating device of another system disadvantageously expands the size thereof.